Laboratory of Intracellular Membrane Dynamics, Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan.
Department of Genetics, Graduate School of Medicine, Osaka University, Osaka, Japan.
Autophagy. 2023 Jun;19(6):1869-1871. doi: 10.1080/15548627.2022.2138686. Epub 2022 Nov 11.
Macroautophagy (hereafter autophagy) is a highly conserved intracellular degradation system to maintain cellular homeostasis by degrading cellular components such as misfolded proteins, nonfunctional organelles, pathogens, and cytosol. Conversely, selective autophagy targets and degrades specific cargo, such as organelles, bacteria, . We previously reported that damaged lysosomes are autophagy targets, via a process called lysophagy. However, how cells target damaged lysosomes through autophagy is not known. We performed proteomics analysis followed by siRNA screening to identify genes involved in targeting damaged lysosomes and identified a new E3 ligase complex, involving CUL4A (cullin 4A), as a regulatory complex in lysophagy. We also found that this complex mediates K48-linked poly-ubiquitination on lysosome protein LAMP2 during lysosomal damage; particularly, the lumenal side of LAMP2 is important to recruit the complex to damaged lysosomes. This protein modification is thus critical to initiate the clearance of damaged lysosomes.
自噬（下文简称自噬）是一种高度保守的细胞内降解系统，通过降解细胞成分（如错误折叠的蛋白质、功能失调的细胞器、病原体和细胞质）来维持细胞内的平衡。相反，选择性自噬则靶向并降解特定的货物，如细胞器、细菌等。我们之前曾报道，受损的溶酶体是自噬的靶标，这一过程被称为溶酶体自噬。然而，细胞如何通过自噬靶向受损的溶酶体尚不清楚。我们进行了蛋白质组学分析，随后进行了 siRNA 筛选，以鉴定参与靶向受损溶酶体的基因，并发现了一个新的 E3 连接酶复合物，涉及 CUL4A（Cullin 4A），作为溶酶体自噬的调节复合物。我们还发现，该复合物在溶酶体损伤时介导溶酶体蛋白 LAMP2 上的 K48 连接多泛素化；特别是，LAMP2 的腔侧对于将复合物募集到受损的溶酶体至关重要。因此，这种蛋白质修饰对于启动受损溶酶体的清除至关重要。
